C&P from another site, but good info:

Best Answer - Chosen by Asker
Short answer - Gran Patron (sometimes called Platinum)

Long answer - Patron, while good, is often thought of as the "best" tequila because they spend more marketing dollars than any other tequila company, and thus when college kids are ready to move up from Cuervo, they often go to Patron as they see it advertised so much, and their exploration stops there.

Make no mistake, Patron isn't bad by any means. But you can get better for less.

Whether you're dead set on getting them Patron or open to suggestions, you should know the following:

The aging has a lot to do with the taste and the cost, so make note of how the bottle is labeled. Generally, the longer the aging, the smoother the taste and the more expensive.

Blanco (because it's totally clear) - no aging. Sometimes called silver
Reposado - minimally aged at least 2 months, but can be up to 1 year. Sometimes called gold.
Anejo - heavily aged, minimally 1 year but less than 3 years.

The really expensive ones can even be aged longer than regular anejos, and these are often referred to as ultra anejos. In the Patron family, there's is called Gran Patron (or sometimes referred to as Platinum).

Also consider how he's going to drink it.

Slammed shots - go for a blanco. Anything else is a waste of flavor and $$

Sipped shots (how I recommend it) - go for anejo only and savor with no salt and a squeeze of lime. Chilled or on the rocks is good as is straight.

Margarita - anejo is a waste, especially if he isn't using fresh squeezed lime juice. Go for blanco or reposado.

If you're open to alternatives, any of the following are better, and often cheaper than Gran Patron:

Don Julio 1942
Cuervo Reserva de la Familia (note - this is 1 of 2 good tequilas Cuervo makes. The rest is garbage)
Herradura Seleccion Suprema

If you don't want to spend that much (Gran Patron is over $200 for a 750ml bottle), then I recommend the following in the $50 range:

Corzo
Dos Lunas
Chinaco
Arette
El Tesoro
El Charro